1. Field of the Invention
The invention relates to a process as well as to an apparatus for removing alcohol from beverages. Such de-alcoholizing is used for the production of low-alcohol and/or non-alcoholic beer from ready-to-fill original beer. The de-alcoholizing is preferably done by removing the alcohol, at least partially, through the use of dialysis membranes in dialysis modules which dialysis modules remove alcohol because of the alcohol concentration gradient between the beverage on one side of the membrane and a dialysate on the other side of the membrane.
2. Background Information
In a dialysis module, substances are transferred from one fluid, such as a beverage, to another, the dialysate, through a membrane because of a concentration driving force. The dialysate, which generally has little or no concentration of the substances being removed, is circulated through the dialysis module where the dialysate picks up at least a portion of the substances being removed, which in this case is alcohol. The dialysate, after becoming enriched with alcohol in the dialysis module, can then, if desired, be subsequently fed through an alcohol stripping column, or rectification column, where the dialysate is freed of at least a portion of the diffused alcohol.
In order to maintain the taste of the low-alcohol beverage that is being produced as closely as possible to the taste of the original beverage, it is preferable that the dialysate be chosen such that the dialysate is the low-alcohol beverage so that the only difference between the beverage and the dialysate is the alcohol content. Thus, substantially only alcohol will flow across the dialysis membrane in the dialysis module. It is therefore desirable to maintain all of the ingredients in the dialysate as are present in the beverage, because if an ingredient in the dialysate is removed, ie. in the rectification column, that ingredient can also ultimately be removed from the beverage as well, because that ingredient can now also flow across the dialysis membrane under its own concentration gradient.
The alcohol can be expelled from the dialysate in the rectification column at medium temperatures under vacuum conditions, and the alcohol can then subsequently be condensed in a condenser and discharged from the system. In order to heat the dialysate to the temperature needed for the alcohol removal step, a regenerative heat exchanger is preferably arranged between the dialysis modules and the rectification column. Thus, dialysate of high-alcohol content, going to the rectification column, can be heated to the required inlet temperature by acquiring heat from the dialysate of low-alcohol content coming out of the rectification column.
Because of the comparatively high temperature needed in the rectification column to efficiently remove the alcohol, the dialysate of low alcohol content coming out of the rectification column, which dialysate then enters the feed region of the dialysis column when the dialysate is continuously cycled, has a comparatively high temperature and thus, germs and their corresponding metabolic products can form which could give a disagreeable taste to the beverage being treated. On the other hand, if the temperature in the feed region of the dialysis column is reduced, the temperature of the dialysate entering the rectification column from the dialysis column is usually not high enough and, depending on the composition of the respective beverage being treated, ie. if the beverage being treated were beer, increased foaming would result in the region of the rectification column. Due to this increase in foaming, the valuable substances of the dialysate, and thus ultimately the beverage, could also be removed from the dialysate when the dialysate is subjected to the vacuum conditions for removal of the alcohol. The preferable replacement of these valuable substances in the dialysate would then require repeated enrichment of these substances in the region of the dialysis module, and thus, undesired changing and influencing of the beverage taste would be unavoidable.